1. Field of the Invention
This invention relates to a packaging material for photosensitive materials such as photographic photosensitive materials.
2. Description of the Prior Art
Since the qualities of photographic photosensitive materials are damaged by even small amounts of light, gas or moisture, it is necessary that packaging materials have light-shielding, gas barrier and moistureproofness. Moreover, it is also required to have sufficient heat seal strength and physical strength in order to prevent pinholes, ruptures and punctures, through packaging, stocking and physical distribution.
Heretofore, as the packaging material having such properties, there are cross laminated films using two uniaxially stretched high density polyethylene resin films (U.S. Pat. No. 4,147,291) and laminated films containing a linear low density polyethylene resin film (U.S. Pat. No. 4,452,846).
Incidentally, photographic photosensitive materials placed in a sealing bag are carried in a dark room, and taken out of the bag there. Therefore, the bag cable of opening by hand without using a cutter is preferred in view of safety. However, the above conventional packaging materials are difficult to be opened by hand, though they are excellent in physical strength and heat seal strength. Therefore, the inventor developed a packaging material easily openable by hand composed of an aluminum foil, a light shielding heat seal film layer having a prescribed resin composition laminated to one side of the aluminum foil in a delamination resistance stronger than a prescribed value through an anchor coat layer, and a restricted flexible sheet layer laminated to the other side (U.S. Pat. No. 4,708,896). However, the cost of the above packaging material is increased by the process for providing the anchor coat layer including the loss produced until the coating speed reaches a prescribed value and the loss produced by trimming both sides of the web-shaped packaging material. Moreover, the anchor coat layer is extremely thin, and it is difficult to coat in an uniform thickness resulting in variable openability.